Portable computers such as notebooks and palmtops are popular among computer users who travel and need to take their work along. They are smaller and lighter than laptops, and are therefore more portable. It is currently possible to build very small computers, and to provide a great deal of modularity and therefore flexibility in the application of such machines.
It is known to the inventors, for example, to build a palmtop or notebook computer wherein various modules are inserted into bays and make connection therein to a bus structure. In such modular portable computers the modules provide divisible electronic functions. Taken to the extreme, nearly every independent function may be incorporated into a module as a peripheral. In a modular computer of this sort, the framework without the modules may comprise essentially a bus structure and a power conversion unit. Functional modules may include interchangeable CPUs, memory devices of various sorts, system control logic, peripheral communication devices, I/O devices, and more. Also, modules may assume a wide variety of shapes and sizes, such as the well-known Personal Computer Memory Card International Association (PCMCIA) form factor standards.
The modular concept gives the user a choice of functional configurations in one portable computer. For example, while traveling a user may require a modem but not a floppy disk drive, and the modular concept lets the user select the functions he/she needs. The modular concept also allows a portable computer to be smaller and more portable than it would be if all the functions that might be needed have to be incorporated. Size is a very competitive criterion in commanding market share. The evolution to smaller and lighter modular computers, however, is not without problems.
One of the problems in such a modular computer is dissipating heat from the individual modules. Incorporation of a CPU module into portable computer architecture is very desirable, because it provides ability to tailor the CPU power to other modules and software applications. It also allows a computer owner to upgrade to more powerful CPUs as they become available. However, incorporating a large microprocessor in a module configured for a modular portable computer creates a significant concentration of heat to dissipate.
Heat generation by large microprocessors in functional modules is so great that a prudent approach to packaging is imperative. Also, the conventional approaches of cooling fans and the like are solutions that pose an additional burden in the design of portable computers, requiring more space and larger power supplies. In addition, high running temperature degrades computer performance and can lead to failure. Manufacturers that do not address thermal implications that directly affect CPU performance risk premature microprocessor failures. An overheated CPU can cause various problems, ranging from data corruption to the loss of file-allocation tables to the microprocessor shutting itself down.
It is likely that future trends in development will result in faster, hotter microprocessors, which will require ever more efficient ways to transfer heat to the surroundings. As one example, Intel's new Pentium.TM., scheduled to succeed the 486 family of microprocessors, has about 3 million transistors, producing heat at a high rate, which, if not disposed of properly, can limit chip performance. It is estimated the Pentium CPU will generate as much as 16 watts during operation.
Intel has established a certification procedure with microcomputer manufacturers to qualify general-purpose computers for safe Pentium use, and few manufacturers have enough cooling for full certification. And the contemplated use of these devices in functional modules and other electronic devices for use in portable computers will require extraordinary efforts to remove waste heat.
The present invention addresses the above-described problems particularly pertaining to use of high-performance microprocessors in modular, portable general-purpose computers. What is needed is a method of removing CPU-generated waste heat economically and effectively within the small confines of a modular, portable computer, guaranteeing optimal processing performance, longevity and reliability.